Study on pitting mechanism of rebar rockbolt in highly-mineralized mine water
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摘要: 受地下水侵蚀及开采环境影响,锚杆易发生腐蚀甚至断裂,点蚀等局部腐蚀形式通常是锚杆失效的主要源头。为研究螺纹钢锚杆在腐蚀性矿井水中的点蚀行为,采用金相、电化学及显微视频等手段,观测了4种锚杆点蚀发展过程并初步揭示其形成机制。结果表明,锚杆的点蚀易发生在夹杂物处,夹杂物及界面处基体优先溶解形成界面沟槽并出现局部酸化,从而进一步加速基体和夹杂物的溶解、脱落而形成点蚀坑;采用大小电极极化试验对比验证了界面沟槽对腐蚀的加速作用。Abstract: Corrosion and abnormal failure of rockbolts often occur in the mine water and complex environment.It is found that local corrosion such as pitting is usually the main origin of corrosion failure.Pitting process and mechanism in simulating corrosive mine water of four rockbolts were tested and analyzed with a comprehensive method including metallographic examination, electrochemical experiments and video microscope.The results showed that rockbolt steel was prone to pitting corrosion due to the inclusions.The pitting mechanism was as follows: The inclusions were preferentially dissolved, producing granular corrosion products and forming interface grooves.Local acidification in grooves accelerated the dissolution and exfoliation of matrix and inclusions, which produced etching pits.The acceleration effect of interface grooves on corrosion was verified by the comparison of polarization curves of different electrodes.
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Key words:
- highly-mineralized mine water /
- rebar rockbolt /
- pitting /
- inclusion /
- interface groove
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表 1 锚杆钢材化学成分
Table 1. Chemical composition of rockbolts
试样 元素含量/% C Si Mn P S Cr Ni Mo Cu V HR335 0.28 0.31 0.78 0.026 0.026 0.023 0.017 0.004 0.019 0.003 HR500 0.23 0.37 1.49 0.023 0.028 0.041 0.024 0.007 0.028 0.068 HT600 0.21 0.46 1.52 0.015 0.007 0.022 0.010 0.007 0.013 0.050 HT700 0.23 0.48 1.53 0.010 0.006 0.025 0.009 0.007 0.014 0.047 表 2 非金属夹杂物检验结果
Table 2. Results of nonmetallic inclusion test
锚杆 非金属夹杂物/级 DS A B C D 细 粗 细 粗 细 粗 细 粗 HR335 1 0 0 0 0 0 0.5 0 0 HT600 1 0 0 0 0 0 0.5 0 0 注:A为硫化物类;B为氧化铝类;C为硅酸盐类;D为球状氧化物;DS为单颗粒球状类。 表 3 腐蚀性矿井水离子浓度
Table 3. Ion concentration of corrosive mine water
离子类型 离子浓度/(mg·L-1) 双柳煤矿 红庆河煤矿 K+ 1.42 2.60 Na+ 385 288 Ca2+ 3.96 9.43 Mg2+ 1.20 3.43 Cl- 302 321 SO42- 14.24 203 HCO3- 558 428 CO32- 0 24.06 总矿化度 1 266 1 280 表 4 模拟溶液配比
Table 4. The proportion of simulated solution
溶质 NaCl NaHCO3 Na2SO4 浓度/(mg·L-1) 530 589 601 表 5 大小电极自腐蚀电流密度对比
Table 5. Comparison of self-corrosion current densities between small and large electrode
材料 大电极自腐蚀
电流密度/(A·cm-2)小电极自腐蚀
电流密度/(A·cm-2)HR335 8.9×10-6 1.26×10-5 HR500 6.61×10-6 1.2×10-5 HT600 6.42×10-6 1.5×10-5 HT700 9.8×10-6 1.17×10-5 -
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